1. Field of the Invention
The invention relates generally to the field of metals and metal alloys that can react with hydrogen to form metal hydrides.
2. Description of Related Art
Metals and metal alloys that are capable of reacting with hydrogen to form a hydride are known as hydride formers or simply metal hydrides. Examples of hydride formers include most elemental metals and their associated alloys. Many of these materials have found applications in hydrogen storage, hydrogen recovery from gas mixtures and energy conversion systems. Unfortunately, these materials suffer from two significant disadvantages:
First, when these metals and alloys react with hydrogen repeatedly, they crack into pieces or break into particles as small as fractions of a micron known as "fines." If they are used as membranes or filters separating hydrogen from other gases, such breaking will cause the filter to fail. If they are used in packed columns or beds for hydrogen storage or absorption, such breaking can cause excessive resistance to gas flow or even a blockage.
A second disadvantage to hydride formers is that they are often sensitive to poisons like carbon monoxide and sulfur compounds and to reactive gases like oxygen. Commercial hydrogen streams contain small amounts of these impurities that prevent the application of metal hydrides in those areas.
The prior art is replete with inventions using metal hydrides to filter hydrogen from a diverse gaseous stream. For example, U.S. Pat. No. 3,793,435 to Reilly et al. teaches the use of lanthanum alloy hydrides for separation of hydrogen from other gases. U.S. Pat. No. 4,108,605 teaches the use of metal hydrides to adsorb hydrogen and impurities from a gaseous stream and then through temperature manipulation to release the hydrogen while retaining the impurities.
While these inventions are useful in purifying hydrogen streams, they still suffer from the physical integrity and impurity sensitivity drawbacks discussed above. Thus, there is room in the art for improvements directed towards improving the dimensional stability and resistance to impurities of metal hydrides.